Our long term goal is prevention and treatment of cancer. In living cells DNA is continuously exposed to damage. Protective mechanisms (such as DNA repair) keep the level of damage low. But still unrepaired damage occurs. This is a problem as unrepaired damage may lead to mutations, and mutations in certain genes lead to cancer. Several reports suggest that individuals with currently unrecognized subtle deficits in their DNA repair capacity are prone to cancer. Unfortunately, detecting these individuals is currently technically challenging and, consequently, these individuals remain undiagnosed. We recently developed a novel technique for the detection of DNA damage. This technology may prove useful not only to measure levels of DNA damage (and therefore estimate cancer risk) but also to estimate the repair capacity of each individual. In the current proposal we have two specific aims: Aim 1: To determine if spontaneous DNA damage is increased in mice with major (homozygous mutant) and subtle (heterozygous) genetic defects in two DNA repair pathways crucial for cancer protection (Base Excision Repair, BER, and Nucleotide Excision Repair, NER), and in the corresponding NER deficient human cells. We will use our novel technique to screen and quantify the presence of spontaneous DNA damage in NER defective mice null (xpc-/-) and heterozygous (xpc) for the Xpc gene and in the corresponding human cells (both xpc-/- and xpc). The study will also be extended to mice compromised in BER (oggl-/- and oggl). Aim 2: To further validate and critically test the types of DNA damage detected by our novel technology. To further validate the types of DNA damage detected by our novel technology, we will study synthetic DNA oligonucleotides containing chemically known lesions, at a specific position, as well as yeast strains defective in NER and BER. Finally, we will use a reported assay (QPCR) to measure the levels of spontaneous DNA damage in the NER- and BER- mutant mice. Data derived from these experiments will provide solid validation for the quantitative and qualitative detection capacity of our technology. Our studies have the potential to improve knowledge of the causes, risk factors, diagnosis, prevention and treatment of cancer using innovative methods. In the future, several other potential uses for our DNA damage detection assay can be anticipated, including evaluation of dietary or therapeutic approaches to reduce cancer risk. [unreadable] [unreadable] [unreadable]